Turbine-rotor.



0. D. H. BENTLEY.

I TURBINE ROTOR. APPLICATION FILED 0CT.23, 19l2.-

Patented Dec. 28, 1915.

OLIVER D. H. BENTLEY, 015 BOSTON, MASSACHUSETTS, ASSIGNOR TO B. F.STURTEVANT COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OFMASSACHUSETTS.

TURBINE-ROTOR.

Specification of Letters Patent.

Patented Dec. 26, T9915.

Application filed October 23, 1912. Serial No. 727,343.

To all whom it may concern: I

Be it known that I, OLIVER D. H. BENT- LEY, a citizen of the UnitedStates, residing at Hyde Park, Boston, in the county of Suffolk andState of Massachusetts, have invented certain new and usefulImprovements in Turbine-Rotors; and I do hereby declare the following tobe a full, clear, and exact description of the invention, such as willenable others skilled in the art to which it appertains to make and usethe same.

The present invention relates to improvements in turbine rotors.

Turbine rotors and similar elements which run at high rotative speedsmust be not only statically balanced so that the center of mass lies inthe axis of rotation, but must also be dinamically balanced so that nounbalanced centrifugal forces will exist which would set up a couple atright angles to the axis of rotation. Turbine rotors are usuallystatically balanced by mounting them on two parallel knife blades andremoving metal until there is no tendency of the rotor to roll on theknife blades. It is much more difficult to dynamically balance a rotor.In some instances, the high speed rotor has been mounted upon a flexibleshaft which bends sufficiently under the couple set up by thedynamically unbalanced condition of'the rotor to allow the rotor to bedynamically self-balanced. In other instances the rotor is rigidlymounted upon a rigid shaft and then is carefully machined into a shapewhich, as far as' care in workmanship can attain, is symmetrical aboutthe axis of the shaft. In this case the stresses set up because of anydynamically unbalanced condition, which machining is unable to obviate,is withstood by the strength of the rotor structure and the shaftbearings. The complications and disadvantages involved in the use of aflexible shaft on a turbine rotor have been considerable, so great infact that in all cases where it was possible to avoid the use of theflexible shaft it has been eliminated, so that the flexible shaft isused only in certain types of turbines having extremely rapid runningand light rotors. The expense and degree of care necessary to machine arigid rotor mounted on a rigid shaft to a symmetrical condition are verygreat and even with the most careful workman- 'sists of two disk-likeplates 3 ship it is found almost impossible to machine a rotor forperfect dynamic balance.

The object of the present invention is to produce a turbine rotor ofsuch construction as in a state of rotation to automatically assume acondition of dynamic balance, and to this end the invention consists inthe turbine rotor hereinafter described and particularly defined in theclaims.

In the accompanying drawings illustrating the preferred form of theinvention Figure 1 is a side elevation of a portion of said rotor, andFig. 2 is a sectional elevation of a turbine rotor embodying thepreferred form of the invention.

The illustrated embodiment is described as follows: The rotor shaft 1,mounted in rigid bearings in the casing, has secured upon it the hub 2of the rotor, which conand 4c supporting at their periphery between themthe blades 5. The plates 3 and 4: are circular in form. They have holesat their centers through which extends the boss 6 of the hub 2. Thecentral holes in the plates 3 and 4 fit the boss 6, and the plates 3 and4 are thereby centered on the shaft. A hexagonal nut 7 screwed upon theboss 6 holds the plates 3 and 4: in position. From the center the platesdiverge from each other to their periphery, as seen in Fig. 2, where theseries of blades 5 is supported. These blades v5 are made of extrudedmetal, and are cut from bars of uniform section and indefinite length,after which they have turned upon their ends the pins 8 which arereceived in the holes spaced around the disks 3 and t in the peripheriesof the disks to receive them. These holes are slightly counter-sunk onthe outside, and the studs 8 are riveted into the counter-sinks in orderto secure the blades in position in the disks. In order securely to holdthe blades from accidental turning in the plates, each counter-sink isscored with a radial groove. "When the ends of the studs 8 are rivetedin the counter-sinks,

the metal of the studs flows into such scores.

and securely holds the blades from turning. The rotor illustrated in thedrawing is intended to receive the steam from the expanding nozzle ornozzles upon its periphery and to discharge it into its center, whenceit escapes through the openings 9 in the disks 3 by a continuous wreathof nozzles, the exhaust will be through the disks 3 and 4, but

where the nozzles are separated, the exhaust, or' part of the exhaust,will or may be thrgrtgh the inoperative inter-blade spaces.

his to be observed that the rotor is of triangular cross-section, and issupported atthe apex of the cross-section; This construction lendsitself to facility of springing of the plates 3 and 4 during therotation of the rotor in order to enable the rotor to bring itself intoa condition of dynamic balance. While the greatest of care is exercisedin the construction of these rotors, it is a matter requiring the utmostnicety of workmanship in order to secure the static balance of thestructure, let alone the dynamic balance, and so the rotor of thepresent invention, being one which self-actingly brings itself to acondition of dynamic balance, contributes substantially to theexcellence of running, conditions of the engine. In the case of a rigidrotor out of dynamic balance when rotated at the high speed incident tothe operation of the turbine, .even if the parts are strong enough tostand the stresses to which they are subjected, the unbalanced conditionsubjects the parts to excessive and unpermissible wear, which hasoperated in many cases to forbid the use of speeds which in the case ofa heavy self-centering dynamically balanced rotor would not only bepermissible but highly desirable, because of the higher speeds capableof being obtained,

' and the excellence of the running conditions of a dynamically balancedrotor.

The gist of the present invention resides in making the rotor flexible,so that it may in operation automatically assume a condi- 1 tion ofdynamic balance.

The present lnvention is not limited to the illustrated embodiment, asit may be eming from their point bodied in other forms within the scopeof the following claims 1. A turbine rotor for turbine engines having arigid shaft and a flexible dynamically self-balancing rotor consistingof a hub on the shaft, a series of blades, and two sheet metal disk-likeplates for connecting the hub and the blades, said plates diverg ofjunction at the hub to their point of junction at the blades.

2. A turbine rotor for turbine engines having a rigid shaft, a hub onthe shaft, :1 series of blades and two flexible sheet metal disk-likeplates uniting the blades and hub, said plates being contiguous to eachother at their point of junction with the hub, and separate from eachother and receiving the blades between them at their point of junctionwith the blades.

3.'A turbine rotor for turbine engines having a rigid shaft, a hub onthe shaft, a series of blades, and two disk-like plates uniting the hub.and blades, said plates being contiguous at their point of junctionwith the hub, and diverging in straight lines to their point of junctionwith the blades.

4. A turbine rotor for turbine engines having a rigid shaft, a hub onthe shaft, a series of blades and two disk-like plates uniting the. huband blades, said plates forming conical surfaces, with their apexescontiguous and their bases separate.

5. A turbine rotor for turbine engines having a rigid shaft, a hub onthe shaft, a. series of blades and two flexible sheet metal disk-likeplates uniting the blades and hub, said plates forming conical surfaceswith their apexes abutting each other and oppositely directedlongitudinally of the shaft, and having very obtuse angles at theirapexes.

OLIVER D. H. BENTLEY. Witnesses:

HORACE VAN EVEREN, GEORGE E. STEBBINs.

